Vacuum Infusion Process: Step-by-Step Guide for Resin Infusion

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Vacuum Infusion Process: What You Need to Know

Vacuum infusion, also known as resin infusion, is a cost-effective and environmentally friendly process for making high-quality composite parts used in the aviation, marine, and energy sectors, as well as smaller DIY projects like boat-building. It uses vacuum pressure to create quality products and is one of the best methods for molding large structural components. 

What is the Vacuum Infusion Process (VIP)?

The Vacuum Infusion Process (VIP) is a technique that uses vacuum pressure to drive resin into a laminate. Materials are laid dry into a mold, and the vacuum is applied before resin is introduced. The resin is infused into the mold cavity to wet out the materials and core during the vacuum infusion. Carbon fiber and fiberglass are mold materials commonly used for this process.

Benefits of VIP

While hand lamination is faster and relatively easy to execute, vacuum infusion has many advantages. It’s cost-effective, delivers better quality, and is safer for the environment. Vacuum infusion molding forms a closed mold process and reduces the number of styrene emissions, which can pollute the environment when not properly filtered. 

Even though it requires a longer set-up time, bottom-line comparisons reveal that when labor and mold longevity are taken into account, vacuum infusion is quicker because the process (not the set-up) is easier. It also has a lower tooling cost than other closed mold techniques.

During the resin infusion process, the resin is under constant vacuum pressure and is not influenced by manual labor.  Voids are reduced to a minimum, and there is little wastage. With the vacuum infusion process, the fiber content is higher, increasing the stiffness and strength of the resulting product.

Shortcomings of VIP

Most of the disadvantages of vacuum infusion are linked to the process’s long set-up time and general handling. Unlike hand lamination, vacuum resin infusion requires one to strategize and develop the optimal vacuum ports and resin injection locations for each composite that is made.

Furthermore, it also requires an experienced hand and can become expensive if there are continuous vacuum leaks as the entire part will have to be binned. Its cosmetic finish is also not as good as open mold processes due to the fabric print; however, this can be amended using a barrier coat.

At this stage of the process’s development, vacuum infusion is more suited to smaller projects. Too much time is required for applications that need high production rates or more complex processes on a mass scale. This is especially true when multiple-use flexible films or top molds are needed for one-off or large parts. 


Preparation: Everything You Need for the Vacuum Infusion Process 

While it’s not rocket science, resin infusion techniques do require some skill. In large industrial productions, trained technicians oversee the process. However, it is possible to perfect the technique with research and practice. Below are the basic materials and equipment needed: 


Generally, polyester, vinyl ester, and epoxy resin tend to work best. When it comes to fibers, most conventional fabrics can be used, although we’d recommend fiberglass or carbon fiber as the gaps in the material allow the resin to transport well.


There are four main pieces of equipment, besides resins and fibers, needed to successfully carry out the vacuum infusion process.  These include:

Vacuum Pumps

You will need to select the appropriate resin infusion vacuum pump to create the correct pressure. While all pumps require regular oil changes and blowdowns, the type of pump most suited is an oil-sealed, single-stage rotary vane vacuum pump. These pumps are available at most pump manufacturers and are produced by a variety of brands.

Vacuum Tubing

Vinyl tubing is a good choice as it’s strong enough to maintain its form under pressure without collapsing. Tubing with a ½” inner diameter allows for maximum flow during infusion application.

Resin Traps

Resin traps are vital to the safety of the vacuum infusion process as they are placed in line to catch excess resin. If not caught, the resin can destroy your vacuum pump. Large-scale projects usually utilize multiple resin traps.

Spiral Tubing

Spiral tubing is needed for vacuum line extenders or resin feed lines. Make sure you buy tubing that complies with resin infusion standards. 

Step-by-Step Guide to the Vacuum Infusion Process 

Bear in mind that each fiberglass infusion project is unique and will require variation depending on size and scale. Below are the basic steps: 

  1. Prepare the mold: Place good quality mold, reinforcements, and core flow material in the desired position.
  2. Set-up resin and vacuum lines: Ensure the network of lines reaches all areas of the laminate and can drain the resin effectively. 
  3. Attach the vacuum bag: The vacuum bag should be tight but allow enough room for tubing. 
  4. Attach the pump and set up the resin bucket: Ensure your resin bucket is properly secured as the pump will produce a strong suction during the vacuum resin infusion. Turn on the pump once everything is in place.
  5. Clamp off resin line: When the laminate is wet out, you can clamp off the resin line to complete the infusion. 

Have a project that requires vacuum infusion? At Plastic Materials Incorporated, we have a range of products from core materials to tubing to help you put together the ideal vacuum infusion kit. Give us a call or click here to start building your kit today!

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